Integral tilting pad bearing

ABSTRACT

There is disclosed a bearing to support a rotating shaft. The bearing includes a cylindrical housing defining a central opening. A plurality of bearing pads integrally coupled to the housing with each bearing pad having a circumferential surface defining a portion of the central opening. A plurality of pins disposed in a bore defined in the housing, with each pin aligned as a pivot for each corresponding pad. Each pad can tilt about the pin in relation to the rotating shaft. Each pad is coupled to the housing by a pair of webs defined by a plurality of cuts forming a plurality of openings in the housing substantially parallel to a line tangent with the circumferential surface of the pad. Each pin is aligned parallel with the rotating pad.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/787,146, filed Apr. 13, 2007, incorporated herein by reference in itsentirety.

FIELD

The present disclosure relates generally to the field of pad typebearings. More specifically, the disclosure relates to a bearing withintegral movable pads. The bearing may be a hydrostatic movable pad typebearings.

BACKGROUND

Hydrodynamic bearings may include one or more pads that are allowed tomove or “float” between two parts that are moving relative to eachother. The pads are generally trapped in a pocket or chamber between twoparts that move relative to each other. A fluid pressure acts on the padto urge it towards one of the moving parts. In bearings known astilt-pad bearings, the pads are also allowed to pivot such that awedge-shaped film of lubrication can form between the pad and one of themoving parts, for example a rotating shaft. Tilt-pad bearings aredesirable because they provide exceptional stability characteristics.This stability is partially caused by reducing the cross-coupledstiffness of the pads by allowing them to pivot about their own pivotpoints.

However, tilt-pad bearings do have disadvantages. Tilt-pad bearingsgenerally include a large number of moving parts including a housing orshell, pads, and pad pivots. Each of these parts must be machined to avery high tolerance to overcome stacked tolerance of the finishedassembly and yield an acceptable shaft clearance. Such a shortcomingrequires very careful attention to the materials choice, design, andmanufacturing of each of the components of the tilt-pad bearing.

SUMMARY

There is provided a bearing to support a rotating shaft. The bearingincludes a cylindrical housing defining a central opening. The bearingalso includes a plurality of bearing pads integrally coupled to thehousing with each bearing pad having a circumferential surface defininga portion of the central opening. The bearing also includes a pluralityof pins disposed in a bore defined in the housing, with each pin alignedas a pivot for each corresponding pad. Each pad can tilt about the pinin relation to the rotating shaft. Each pad is coupled to the housing bya pair of webs defined by a plurality of cuts forming a plurality ofopenings in the housing substantially parallel to a line tangent withthe circumferential surface of the pad. Each pin is aligned parallelwith the rotating pad.

There is provided a method for enhancing shaft rotation in a bearing.The bearing includes a cylindrical housing defining a central opening. Aplurality of bearing pads are integrally coupled to the housing witheach bearing pad having a circumferential surface defining a portion ofthe central opening. A plurality of pins are disposed in a bore definedin the housing, with each pin aligned as a pivot for each correspondingpad. Each pad can tilt about the pin in relation to the rotating shaft.The method includes determining a force to be exerted on at least onepad in the bearing; determining a deformation of one of the bore and pinfrom the exerted force on the pad; and configuring one of the bore andpin to compensate for the determined deformation. The shaft rotation isenhanced by reducing the stress concentration in one of the bore and pincaused by the determined deformation.

There is also provided a thrust bearing. The thrust bearing includes acylindrical housing defining a central opening. The thrust bearing alsoincludes a plurality of bearing pads integrally coupled to the housingwith each bearing pad having a circumferential surface defining aportion of the central opening. The thrust bearing also includes aplurality of pins disposed in a bore defined in the housing, with eachpin aligned as a pivot for each corresponding pad. The thrust bearingalso includes a thrust collar coupled to the rotating shaft aligned withthe bearing pads. Each pad can tilt about the pin in relation to therotating shaft. Each pad is coupled to the housing by a pair of websdefined by a plurality of cuts forming a plurality of openings in thehousing substantially normal to the rotational axis of the shaft. Eachpin is aligned normal to the rotating shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of an exemplary embodiment of a bearingincluding a tilt-pad integral with a support structure.

FIG. 2 is a top plan view of the bearing illustrated in FIG. 1, with thesupport structure including two portions.

FIG. 3 is a perspective view of one portion of the bearing structureillustrated in FIG. 2.

FIG. 4 is an illustration of a tilt pad integral with a supportstructure configured to rotate about a pin positioned in a bore definedin the support structure, including a web having a variablecross-section.

FIG. 5A is a perspective view of an exemplary embodiment of a tilt padintegral with a support structure, the tilt pad configured to rotateabout the x-axis of a pin disposed in the support structure.

FIG. 5B is a sectional view of the tilt-pad illustrated in FIG. 5Aillustrating the geometric shape of the pin and bore defined in thesupport structure.

FIG. 5C is a sectional view of a tilt pad integral with a supportstructure, with a pin including a spherical surface disposed in acylindrical bore in the support structure, the tilt pad configured torotate about the x-axis and y-axis of a pin disposed in the supportstructure.

FIG. 5D is a perspective view of an exemplary embodiment of a tilt padintegral with a support structure, the tilt pad configured to rotateabout the x-axis of a pin disposed in the support structure. The pin isreceived in a bore with a non-circular cross-section.

FIG. 5E is a sectional view of the tilt-pad illustrated in FIG. 5Dillustrating the geometric shape of the pin and bore defined in thesupport structure.

FIG. 6 is a perspective sectional view of a tilt pad integral with asupport structure, the support structure defines a bore configured toreceive a pin.

FIG. 7 is a perspective sectional view of a tilt pad integral with asupport structure, including a pin configured to reduce stressconcentration in the tilt pad when under load.

FIG. 8A is an illustration of a tilt pad integral with a supportstructure configured to rotate about a pin positioned in a bore definedin the support structure on a radial center line of the tilt pad.

FIG. 8B is an illustration of a tilt pad integral with a supportstructure configured to rotate about a pin positioned in a bore definedin the support structure on a radial line offset a pre-selected anglefrom radial center line of the tilt pad.

FIG. 9 is a perspective view of a thrust bearing including a pluralityof tilt pads integral with a support structure, a thrust collar, and arotating shaft.

FIG. 10A is a top plan view of an exemplary embodiment of the bearingillustrated in FIG. 9 including a tilt-pad integral disposedlongitudinally in a bearing support structure.

FIG. 10B is a sectional view of the bearing support structureillustrated in FIG. 10A, including two integral tilt pads.

FIG. 11A is a top plan view of the bearing illustrated in FIG. 9, withthe support structure including two portions.

FIG. 11B is a sectional view of the bearing illustrated in FIG. 11A.

FIG. 12 is a top plan view of an exemplary embodiment of a bearingincluding a plurality of longitudinal and radial orientated tilt padsintegral with a support structure.

FIG. 13 is a top plan view of the bearing illustrated in FIG. 12, withthe support structure including two portions.

FIG. 14A is an exemplary embodiment of a tilt pad integral with asupport structure configured to pivot about a pin positioned in a boredefined in the support structure.

FIG. 14B is a cross section of an exemplary embodiment of a tilt padintegral with a support structure configured to pivot about a pinpositioned in a bore defined in the support structure.

FIG. 15 is a schematic illustration of tilt pad integral with a supportstructure, including oil disposed in a slots defined in the supportstructure, with the oil pressure producing a force proportional to tiltpad rotational velocity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a bearing 10 is shown according to an exemplaryembodiment. The bearing 10 is a generally cylindrical body that isconfigured to radially support a rotating shaft 5. The bearing 10includes a cylindrical housing 20, one or more bearing pads 40 coupledto the outer housing 20, one or more pins 50 trapped between the bearingpads 40 and the housing 20, and may include a fluid between the othercomponents.

The housing 20 (e.g., pad support structure, shell, etc.) provides themain body of the bearing 10. The housing 20 forms a central opening 22that receives the rotating shaft 5. According to various exemplaryembodiments, the housing 20 may be a single body or may be split intotwo or more segments as shown in FIGS. 2-3 and coupled together aroundthe rotating shaft 5.

One or more bearing pads 40 (e.g., tilt pads, rotational pads, etc.) areintegrally formed with the housing 20 and are arranged radially aroundthe central opening 22. Each bearing pad 40 includes a circumferentialsurface 42 that defines a portion of the central opening and supportsthe rotating shaft 5 and a pair of side walls 43. The side walls 43 maybe substantially normal to the circumferential surface 42 or may beangled relative to the circumferential surface 42. If the side walls 43are slanted inward at an angle β, as shown in FIG. 8A, the geometry ofthe housing 20 will retain the bearing pad 40 even if the bearing pad 40breaks away from the housing 20. The bearing pads 40 are coupled to thehousing 20 with a pair of thin members or webs 44 (e.g., walls, struts,arms, etc.) and are allowed to move relative to the housing 20.Integrally forming the bearing pads 40 and the housing 20 as a singleunitary body provides several advantages. With a single body it ispossible to achieve tighter tolerances between the bearing and therotating shaft than is generally possible with a bearing with separatelymachined and assembled components. The webs 44 help to reduce bearingpad flutter by providing a selectable predetermined minimal rotationalstiffness to the bearing pads 40. The webs 44 further provide amechanism to retain the bearing pads 40 within the housing 20.

According to an exemplary embodiment, the bearing pads 40 and webs 44are formed by a multitude of gaps or cuts 28. The cuts 28 that form thewebs 44 are generally parallel to a line tangent to the circumferentialsurface 42 of the bearing pad 40. According to one exemplary embodiment,the bearing is formed from a single solid body and the cuts may beformed by any suitable method, including but not limited toelectro-discharge machining (EDM), electrochemical machining (ECM),laser cutting, water cutting, or conventional machining. According toother exemplary embodiments, the bearing may be formed in another way,such as casting, injection molding, powder metal die casting, orextrusion.

According to one exemplary embodiment, the cuts 28 in the housing 20 andthe webs 44 are a generally constant thickness. Referring to FIG. 4 andaccording to another exemplary embodiment, the thickness of the webs 144may vary along the length of the webs 144. Varying the thickness of thewebs may be desirable in some embodiments to achieve the desired bearingpad stiffness, minimize the stresses in the webs, and increase thefatigue life of the webs.

The webs 44 extend outward from a generally cylindrical bore 24 formedin the housing 20 disposed between the bearing pad 40 and the housing20. A pivot or pin 50 is received in the bore 24 provides one or moreaxis about which the bearing pad 40 rotates relative to the housing 20.The pivot 50 is an elongated member that provides a high stiffnessbehind the pad 40 and a single axis or multiple axis about which thebearing pad 40 can rotate. The shape of the pin 50 may be manipulated toprovide a point, near point, line or area contact between the bearingpad 40 and the pin 50. The pin 50 may be formed from a hardened metal orother material depending on the stiffness desired.

According to one exemplary embodiment, as shown best in FIGS. 5A and 5B,the pin 50 may be cylindrical with a diameter that is constant along thelength of the pin 50. The pin 50 is received in a generally cylindricalbore 24. The bearing pad 40 is allowed to rotate about the x-axis 52 ofthe pin 50.

The bore 24 may have a non-circular cross-section. As shown in FIG. 8A,the bore 24 may have an first portion 24 a that is opposite of thebearing pad 40 and a second portion 24 b that is proximate to thebearing pad 40. According to an exemplary embodiment, the first portion24 a has a diameter that is less than or equal to the diameter of thepin 50 so that there is an interference fit between the pin 50 and thefirst portion 24 a of the bore 24. The second portion 24 b has adiameter that is greater than the diameter of the pin 50 so that thebearing pad 40 pivots on the pin 50 instead of sliding along the pin 50.As the diameter of the second portion 24 b approaches infinity, as shownin FIGS. 5D-E, it may form a substantially flat surface.

According to another exemplary embodiment, and shown best in FIG. 5C,the pin 150 has a varied diameter and a spherical longitudinalcross-section. The bearing pad 40 is allowed to rotate about both thex-axis 52 of the pin 150 and the y-axis 54 of the pin 150. Anotherembodiment provides a non-constant bore with a pin defining acylindrical, longitudinal cross-section allowing the pin to tilt aboutthe x-axis and the y-axis of the pin since the bore diameter variesalong its length. According to still another exemplary embodiment, shownbest in FIG. 6, the bearing 10 may have no pin in the bore 24. With nopin in the bore 24, the bearing pad 40 is allowed to rotate about thex-axis 52, rotate about the y axis 54 and translate along the z-axis 56.If the pin material is varied, the motion along the x-axis can beinfluenced.

According to still another exemplary embodiment, shown in FIG. 7, thebearing 10 may include a bore 224 and a pin 250 that are configured toreduce the stress concentration around the bore 224 when the rotatingshaft 5 deforms the bearing pad 240. When a load is applied to thebearing pad 240, it tends to compress which flattens or otherwise deformthe bore 224. Using finite element analysis (FEA) or another suitableanalysis, the deformed shape may be anticipated. Instead of a linear,oval, elliptical or other formula-based shape, the pin 250 and bore 224are created to match the FEA model or free-form shape. Anticipating andcompensating for the deformation of the bore 224 helps to ensure properpad rotation and stiffness.

The location of the bore 24 relative to the radial centerline 46 of thebearing pad 40 may be varied. Referring to FIG. 8A and according to oneexemplary embodiment, the bore 24 is located generally aligned with theradial centerline 46 of the bearing pad 40. Referring to FIG. 8B andaccording to another exemplary embodiment, the bore 24 may be locatedoffset to one side at an angle γ, that is greater than the angle θ ofthe radial centerline 46.

The placement and configuration of the bores and the configuration ofthe pins may be the same for all bearing pads in the bearing or may beunique depending on the bearing application.

According to another exemplary embodiment, as shown in FIGS. 9-11B, thebearing may be a thrust bearing 310 and longitudinally support arotating shaft 5. The bearing 310 includes a cylindrical housing 320,one or more bearing pads 340 coupled to the outer housing 320, one ormore pins 350 trapped between the bearing pads 340 and the housing 320,a thrust collar 360 that is aligned with the housing 320 and traps thebearing pads 340 between the thrust collar 360 and the housing 320, andmay include a fluid between the other components.

The main housing is a generally cylindrical body that defines a centralopening 322 configured to receive a rotating shaft 5. The bearing pads340 are provided on one of the faces of the housing 320 and support thethrust collar 360. Bearing pads 340 are similar to bearing pads 40 andinclude a circumferential face 342 that defines a portion of the centralopening 322. The bearing pads 340 are coupled to the main housing 320with a pair of webs 344 defined by a multitude of cuts 328 in thehousing 320. According to various exemplary embodiments, the housing 320may be a single body as shown in FIGS. 9-10B or may be split into two ormore segments as shown in FIGS. 11A-B and coupled together around therotating shaft 5. The pins 350 are received in bores 324 formed in thehousing 320 and are oriented generally normal to the rotating shaft 5received by the central opening 322.

According to other exemplary embodiments, the bearing 410 may be acombination thrust and radial bearing and may have a first set ofbearing pads 440 that radially support a rotating shaft 5 and a secondset of bearing pads 441 that longitudinally support a rotating shaft 5.Bearing pads 440 and 441 are integrally formed as a single unitary bodywith the housing 420. The housing 420 may be a single body as shown inFIG. 12 or may be split into two or more segments as shown in FIG. 13.

The bearing pads may have a four-sided profile or may have other variedshapes. As shown in FIG. 14A, the bearing pads 540 coupled to thehousing 520 may have a hexagonal shape. The bearing pads 640 may becoupled to the housing 620 with stepped webs 644, as shown in FIG. 14B.

Any of the bearings described above may include attributes common inhydrodynamic bearings (e.g., flooded lubrication, directed lubrication,hydrostatic support features, etc.). As shown in FIG. 15, oil or anotherfluid, for example process fluid used in lubricated hydrodynamicbearings, may be diverted to, supplied to, or trapped in the cuts thatform the bearing pads and webs. The fluid, for example oil, is routed tothe cuts through conduits defined in the housing of the bearing, theconduits are in fluid communication with a source of fluid and the cutsare formed in the housing by well known methods. The oil is compressedas the bearing pad rotates about the pin, which increases the pressureof the oil in the compressed cuts. The increased pressure produces adamping force that opposed the force rotating the bearing pad andproportional to the rotational velocity of the rotating shaft. Thedampening force further reduces pad flutter.

While the embodiments shown in the FIGURES illustrate a bearing that isgenerally shown as being formed from a single body or two halves formedfrom a single body, it should be understood that many variations arepossible. According to other exemplary embodiments, the bearing may beformed from a combination of materials that are coupled or fastenedtogether. The bearing material can be metal, plastic, wood, compositematerials, sintered powder metal, self lubricating materials, or anyother suitable material.

For purposes of this disclosure, the term “coupled” means the joining oftwo components (electrical or mechanical) directly or indirectly to oneanother. Such joining may be stationary in nature or movable in nature.Such joining may be achieved with the two components (electrical ormechanical) and any additional intermediate members being integrallyformed as a single unitary body with one another or with the twocomponents or the two components and any additional member beingattached to one another. Such joining may be permanent in nature oralternatively may be removable or releasable in nature.

Describing the bearing with Figures should not be construed as imposingon the bearing any limitations that may be present in the Figures. Thebearing contemplates methods, systems and program products on anymachine-readable media for accomplishing its operations. The embodimentsof the bearing may be implemented using an existing computer processors,or by a special purpose computer processor, incorporated for this oranother purpose or by a hardwired system.

The foregoing description of embodiments of the bearing has beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the bearing to the precise formdisclosed, and modifications and variations are possible in light of theabove teachings. The embodiments were shown and described in order toexplain the principals involved and its practical application to enableone skilled in the art to utilize the bearing in various embodiments andwith various modifications as are suited to the particular usecontemplated.

It is also important to note that the construction and arrangement ofthe elements of the bearing as shown in the preferred and otherexemplary embodiments is illustrative only. Although only a fewembodiments of the present inventions have been described in detail inthis disclosure, those skilled in the art who review this disclosurewill readily appreciate that many modifications are possible (e.g.,variations in sizes, dimensions, structures, shapes and proportions ofthe various elements, values of parameters, mounting arrangements, useof materials, colors, orientations, etc.) without materially departingfrom the novel teachings and advantages of the subject matter recited.For example, elements shown as integrally formed may be constructed ofmultiple parts or elements show as multiple parts may be integrallyformed, the operation of the interfaces (e.g. clamps, etc.) may bereversed or otherwise varied, the length or width of the structuresand/or members or connector or other elements of the system may bevaried, the nature or number of adjustment positions provided betweenthe elements may be varied (e.g. by variations in the number ofengagement slots or size of the engagement slots or type of engagement).It should be noted that the elements and/or assemblies of the system maybe constructed from any of a wide variety of materials that providesufficient strength or durability, in any of a wide variety of colors,textures and combinations. Accordingly, all such modifications areintended to be included within the scope of the bearing. Othersubstitutions, modifications, changes and omissions may be made in thedesign, operating conditions and arrangement of the preferred and otherexemplary embodiments.

1. A bearing to support a rotating shaft comprising: a cylindricalhousing defining a central opening; a plurality of bearing padsintegrally coupled to the housing, each bearing pad having acircumferential surface defining a portion of the central opening; and aplurality of pins disposed in a bore defined in the housing, with eachpin aligned as a pivot for each corresponding pad, wherein each pad cantilt about the pin in relation to the rotating shaft.
 2. The bearing ofclaim 1, wherein each pad is coupled to the housing by a pair of websdefined by a plurality of cuts forming a plurality of openings in thehousing substantially parallel to a line tangent with thecircumferential surface of the pad.
 3. The bearing of claim 1, whereineach pin is aligned parallel with the rotating shaft.
 4. The bearing ofclaim 1, wherein the bore has a constant diameter and the pin defines acylindrical, longitudinal cross-section, wherein the pad can tilt aboutthe x-axis of the pin.
 5. The bearing of claim 1, wherein the bore has aconstant diameter and the pin defines a spherical, longitudinalcross-section, wherein the pad can tilt about the x-axis and y-axis ofthe pin.
 6. The bearing of claim 1, wherein the bore and pin areconfigured to reduce stress concentrations in the bearing.
 7. Thebearing of claim 1, wherein the bore and pin are offset from the radialcenterline of the pad.
 8. The bearing of claim 2, wherein each webvaries in thickness as defined by the cuts in the housing.
 9. Thebearing of claim 2, including a fluid in each opening and furtherincluding a fluid delivery passage extending through the housing and influid communication with each opening, wherein the fluid permits activecontrol of the pad position and pad damping characteristics.
 10. Thebearing of claim 9, wherein the fluid is oil.
 11. A method for enhancingshaft rotation in a bearing, the bearing including a plurality ofbearing pads arranged circumferentially around a central opening in abearing housing, with each bearing pad integrally coupled to the housingwith a plurality of webs, and a plurality of pins disposed in a boredefined in the bearing housing, each pin aligned as a pivot for eachcorresponding pad, wherein each pad can tilt about the pin in relationto a rotating shaft, the method comprising: determining a force to beexerted on at least one pad in the bearing; determining a deformation ofone of the bore and pin from the exerted force on the pad; andconfiguring one of the bore and pin to compensate for the determineddeformation, wherein the shaft rotation is enhanced by reducing thestress concentration in one of the bore and pin caused by the determineddeformation.
 12. The method of claim 11, including the step ofconfiguring the pin as a cylinder.
 13. The method of claim 11, includingthe step of configuring the pin with a spherical surface.
 14. The methodof claim 11, including the step of varying the thickness of the websassociated with one of the bearing pads.
 15. The method of claim 11,including the step of injecting a fluid into a gap defined by the pad,the webs and the housing.
 16. The method of claim 15, wherein the fluidis oil.
 17. A thrust bearing comprising: a housing defining a centralopening, the opening configured to receive a rotating shaft; a pluralityof bearing pads integrally coupled to the housing, each bearing padhaving a circumferential surface defining a portion of the centralopening; a plurality of pins disposed in a bore defined in the housing,with each pin aligned as a pivot for each corresponding pad; and athrust collar coupled to the rotating shaft and aligned with the bearingpads, wherein each pad can tilt about the pin in relation to therotating shaft.
 18. The thrust bearing of claim 17, wherein each pad iscoupled to the housing by a pair of webs defined by a plurality of cutsforming a plurality of openings in the housing substantially normal tothe rotational axis of the shaft.
 19. The bearing of claim 17, whereineach pin is aligned normal to the rotating shaft.
 20. The bearing ofclaim 17, wherein the bore has a constant diameter and the pin defines acylindrical, longitudinal cross-section, wherein the pad can tilt aboutthe x-axis of the pin.
 21. The bearing of claim 17, wherein the bore hasa constant diameter and the pin defines a spherical, longitudinalcross-section, wherein the pad can tilt about the x-axis and y-axis ofthe pin.
 22. The bearing of claim 17, wherein the bore has anon-constant diameter and the pin defines a cylindrical, longitudinalcross-section, wherein the pad can tilt about the X-axis and Y axis ofthe pin.
 23. The bearing of claim 18, including a fluid in each openingand further including a fluid delivery passage extending through thehousing and in fluid communication with each opening, wherein the fluidpermits active control of the pad position and pad dampingcharacteristics.
 24. The bearing of claim 22, wherein the fluid is oil.